Serum concentration of hyaluronan, IgM and IgA rheumatoid factors in a population based study of juvenile chronic arthritis.

Increased serum levels of hyaluronan (HA) have been found in patients with liver diseases, psoriasis, malignancies as well as in rheumatoid arthritis and osteoarthritis. In the two latter groups serum HA levels may reflect the extent of synovial involvement and inflammation, rather than only unspecific information. This study was performed to elucidate the value of measuring HA in children with juvenile chronic arthritis (JCA) and to study its relation to class specific rheumatoid factors (IgM Rf and IgA Rf). HA was analysed in sera from 271 patients with JCA and 130 controls using a radiometric assay and IgM Rf and IgA Rf were analysed using an enzyme immunoassay. The results were analysed in relation to JCA subgroup, disease activity and functional outcome. In patients and controls higher levels of HA were found in young children than in older. Raised levels of HA and IgM Rf were mainly found in children with polyarticular disease. Impaired functional outcome was related to raised HA levels. No correlation was found between HA levels and IgM Rf or IgA Rf. Measurement of HA levels in JCA is of no diagnostic value because of low sensitivity. Quantification of HA may, however, have prognostic value in a subgroup of patients belonging to the polyarticular subgroup.